Question

Give reasons why the gauche conformation of butane would show a lower energy at a dihedral angle greater than 60 degrees

Answer 1

In the Gauche conformation , the relationship between two atom or groups whose dihedral angle exist between .That means the dihedral angle is more than and less than

In the case of Butane, the rotation greater than will help to move the methyl group far further apart from each other especially the and carbon atoms. which will give the maximum stability to the molecule and result of decrease of the energy. The reason behind this conformation is torsional strength or the presence steric strength which prevent to form the steric hindrance.